The goal of the proposal is to examine the general hypothesis that testosterone normalization in the burned patients will ameliorate the severe net catabolic state of the skeletal muscle and promote recovery during both the acute and the recovery phases of the burn treatment. The efficiency of testosterone normalization will be addressed by the rate of protein synthesis and breakdown, lean body mass, muscle mass and muscular strength. Protein synthesis and breakdown in the skeletal muscle will be determined by two independent methods using stable isotope tracers: either a direct incorporation of isotopes into the proteins, or an A-V balance model of both tracer and tracee combined with muscle biopsy to evaluate the enrichment of the tracers in the muscle. The studies will be conducted in burn patients during their acute phase of hospitalization, with the control study conducted about one week after admission and the intervention study after 2-3 weeks of testosterone injection. The studies will also be conducted in three convalescent groups of burn patients receiving: (a) standard rehabilitation; (b) testosterone + standard rehabilitation and (c), testosterone + resistance exercises throughout two months of rehabilitation. These studies will provide new insight into the anabolic effects of testosterone normalization on the regulation and repair of burn injury-induced skeletal muscle protein metabolisms during both acute and rehabilitation phases of burn treatment.